This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2000-208355, filed Jul. 10, 2000, the entire contents of which are incorporated herein by reference.
1. Field of the Invention
The present invention relates to a semiconductor device, particularly, to a hot plate for heating a semiconductor substrate or wafer held by an electrostatic chuck and a method of manufacturing a semiconductor device using the particular hot plate.
2. Description of the Related Art
In manufacturing a semiconductor device, a semiconductor circuit is formed by repeating the steps of forming an insulating film and a conductive film on a semiconductor substrate or wafer (hereinafter xe2x80x9cwaferxe2x80x9d) such as a silicon substrate by a sputtering method, a CVD (Chemical Vapor Deposition) method, etc., and etching these films for the patterning purpose. Chemical reactions are utilized for the deposition and etching of the film, and the deposition rate and the etching rate are affected by the temperature. The quality of the deposited film is also affected by the temperature. It follows that it is important to control appropriately the temperature of the wafer under processing in order to carry out the processing stably with good reproducibility.
It is widely known to the art that the front surface or the back surface of a wafer is irradiated with light emitted from an infrared ray lamp for heating the wafer. In the case of using an infrared ray lamp, however, it is difficult to control accurately the temperature because the absorption efficiency of the infrared ray differs depending on the kind of the film formed on the wafer. What should also be noted is that, since the cooling cannot be achieved, the temperature tends to be excessively elevated during the processing.
Under the circumstances, a hot plate having a resistance heater arranged therein has come to be used widely. To be more specific, the particular hot plate is fixed to a stage equipped with a cooling mechanism, and a wafer is disposed on the hot plate. In this case, the wafer is heated or cooled by utilizing the heat conduction. The particular system includes the method that the wafer is tightly attached to the hot plate by utilizing the evacuation on the back surface of the wafer so as to fix the wafer, the method that the wafer is electrically fixed by utilizing the electrostatic attracting force, and the method that the wafer is mechanically pushed against the hot plate by utilizing a clamp or the like for fixing the wafer. Among these methods, it is impossible to employ under the vacuum the evacuation on the back surface. Also, in the case of utilizing the mechanical clamping force, the pushing member tends to cause the dust generation. Specifically, it is possible for a film to be attached to the pushing member. It is also possible for the pushing member to be brought into mechanical contact with the wafer. In this case, rubbing is brought about because a mechanical force is applied to the pushing member so as to generate dust.
In view of the above-noted problems inherent in the prior art, the method of allowing the wafer to be electrostatically held on a hot plate of an electrostatic chuck type is widely employed in recent years so as to carry out the heating and the cooling.
However, in the case of allowing the wafer of room temperature to be electrostatically held on the conventional electrostatic chuck type hot plate having a high temperature, serious problems are generated. For example, the wafer tends to be cracked. Also, it is difficult to dispose accurately the wafer on the hot plate.
FIGS. 17 and 18 are cross sectional views each showing the conventional electrostatic chuck type hot plate. FIG. 17 shows the state in the chucking step, with FIG. 18 showing the state in the chuck-releasing step. The electrostatic chuck type hot plate comprises a plate body 100 formed of, for example, alumina. A heater electrode (heat generating electrode) 101 formed of, for example, a tungsten wire is arranged in substantially the central portion in the thickness direction of the plate body 100. Also, an electro-static chuck electrode 102 is arranged in a region close to the surface of the plate body 100 on which a wafer 103 is disposed.
Where the wafer 103 of room temperature is disposed and chucked on the hot pate having a high temperature, the wafer 103 is thermally expanded in accordance with the temperature elevation. However, since the wafer 103 is fixed to the entire surface of the plate body 100 by the electrostatic chucking force, the wafer 103 fails to be expanded sufficiently as shown in FIG. 17, with the result that the wafer 103 is finally cracked by the compression stress. Particularly, if the hot plate has a high temperature, the wafer 103 is much expanded thermally so as to promote the cracking of the wafer 103.
As described above, the wafer 103 is cracked by the compression stress in the case where the wafer 103 of room temperature is chucked on the conventional electrostatic chuck plate having a high temperature. Also, dust is generated by the rubbing, and the transfer error is generated by the deviation of the wafer 103. What should also be noted is that the electrostatic chucking force is changed depending on the kind of the film formed on the back surface of the wafer, with the result that the frequency of the crack occurrence differs depending on the kind of the film formed on the back surface of the wafer 103.
Further, the degree of discharge in the chuck releasing step also differs depending on the kind of the film formed on the wafer. Therefore, the wafer releasing process continues to operate even if the chucking force is not eliminated completely, thereby bringing about a transfer deviation (jumping) as shown in FIG. 18. In order to overcome the difficulty, the wafer is held on the hot plate before application of the chuck voltage and, after heated to some extent to permit the thermal expansion, the wafer is chucked on the hot plate. Alternatively, the chuck-releasing time is set long. However, these methods give rise to the problem that the through-put is markedly lowered. Also, where it is necessary to start the film formation during the temperature elevation of the wafer as in the Al reflow process, the Al filling properties are deteriorated so as to lower the yield.
According to a first aspect of the present invention, there is provided a hot plate comprising: a plate body having a convex surface on which a semiconductor substrate is disposed; a heat generating electrode formed within the plate body; and an electrostatic chuck electrode formed in the plate body, wherein a distance between the semiconductor substrate and the convex surface of the plate body is increased from a central portion toward an outer peripheral portion of the plate body, when the semiconductor substrate is disposed on the convex surface of the plate body.
According to a second aspect of the present invention, there is further provided a hot plate comprising: a plate body having a substantially flat surface on which a semiconductor substrate is disposed; a heat generating electrode formed within the plate body; and an electrostatic chuck electrode formed in the plate body in a convex scheme over the range from one outer peripheral portion to the opposite outer peripheral portion of the plate body via the central portion.
According to a third aspect of the present invention, there is further provided a method of manufacturing a semiconductor device, comprising: disposing a semiconductor substrate on a hot plate including a plate body, a heat generating electrode formed in the plate body and configured to heat the semiconductor substrate disposed on the hot plate, and an electrostatic chuck electrode formed in the plate body and divided into a plurality of electrode portions over the range from one outer peripheral portion to the opposite outer peripheral portion of the plate body via the central portion to include an inner circumferential electrode portion and an outer circumferential electrode; holding the semiconductor substrate on the hot plate by a chucking force generated by applying a chuck voltage to the electrostatic chuck electrode successively from the inner circumferential electrode portion toward the outer circumferential electrode portion to generate the chucking force successively from the inner circumferential electrode portion toward the outer circumferential electrode portion temperature; and processing the semiconductor substrate heated on the hot plate.
According to a fourth aspect of the present invention, there is further provided a method of manufacturing a semiconductor device, comprising: disposing a semiconductor substrate on a hot plate including a plate body, a heat generating electrode formed in the plate body and configured to heat the semiconductor substrate disposed on the hot plate, and an electrostatic chuck electrode formed in the plate body; holding the semiconductor substrate on the hot plate by a chucking force generated by applying a chuck voltage to the electrostatic chuck electrode; processing the semiconductor substrate heated on the hot plate; releasing the semiconductor substrate from the hot plate by applying a chuck-releasing voltage of an opposite polarity to that of the chuck voltage to the electrostatic chuck electrode; and controlling at least one of the chuck voltage, a chucking time, the chuck-releasing voltage, and a chuck-releasing time based on a detected information obtained by detecting a back surface state of the semiconductor substrate before or after disposing the semiconductor substrate on the plate body.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.